EP0177346B1 - Hydraulic master cylinder - Google Patents
Hydraulic master cylinder Download PDFInfo
- Publication number
- EP0177346B1 EP0177346B1 EP85307060A EP85307060A EP0177346B1 EP 0177346 B1 EP0177346 B1 EP 0177346B1 EP 85307060 A EP85307060 A EP 85307060A EP 85307060 A EP85307060 A EP 85307060A EP 0177346 B1 EP0177346 B1 EP 0177346B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- bore
- master cylinder
- reservoir
- valve
- primary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
- B60T11/10—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting by fluid means, e.g. hydraulic
- B60T11/16—Master control, e.g. master cylinders
- B60T11/232—Recuperation valves
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
- B60T11/10—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting by fluid means, e.g. hydraulic
- B60T11/16—Master control, e.g. master cylinders
- B60T11/20—Tandem, side-by-side, or other multiple master cylinder units
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
- B60T11/10—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting by fluid means, e.g. hydraulic
- B60T11/16—Master control, e.g. master cylinders
- B60T11/22—Master control, e.g. master cylinders characterised by being integral with reservoir
Definitions
- This invention relates to a hydraulic master cylinder, and more particularly to a so-called “tandem" master cylinder in which two pistons are arranged in a common bore and pressurise separate primary and secondary pressure chambers which are connected to respective use circuits.
- Such master cylinders are commonly used in split circuit hydraulic brake systems of motor cars.
- a typical tandem master cylinder is shown in published British patent application GB 2030668A. Whilst such master cylinders work effectively they tend to be of considerable length which creates difficulties in housing the master cylinder in a motor car, and are of considerable weight, which is undesirable.
- valve seat In the case of GB 2135412 the valve seat is directly machined on the internal end face of the master cylinder body assembly. Such machining is difficult to achieve with accuracy, and necessitates the provision of a connecting passage located within the thickness of the end wall of the master cylinder. This unnecessarily adds to the length and weight of the master cylinder.
- This problem is in part overcome in GB 1289608A since the recuperation passage is formed in the side-wall of the master cylinder, and the valve seat is formed on a separate end plug.
- the valve seat must be machined accurately over a relatively large area, and in particular must be exactly perpendicular to the master cylinder axis in order to ensure reliable sealing. Further the valve seat is particularly vulnerable to damage, e.g. by scratching, if the end plug is removed.
- the prior art suffers from the further disadvantage that the moving components of the recuperation valve, together with the associated springs and control linkage, are located within the portion of the main bore of the master cylinder which forms the secondary pressure chamber.
- a tandem master cylinder which overcomes some of the problems outlined above is illustrated in DE-B-2711297 (corresponding to the preamble of claim 1).
- the recuperation passage associated with the second pressure chamber extends radially outwardly from the secondary chamber, and a recuperation valve is located outside the zone of the bore of the master cylinder.
- a mechanical connection extends from the recuperation valve into the main bore of the master cylinder to open the recuperation valve when the secondary piston is in its rest position.
- the secondary piston in order to engage the mechanical connection the secondary piston includes a forward extension which projects into the zone of the recuperation passage when the secondary piston is in its rest position.
- the main bore of the master cylinder must be correspondingly lengthened. In effect, the portion of the bore occupied by the secondary piston extension is unavailable for pressure generation, and merely adds to the overall length of the master cylinder.
- the present invention is characterized in that the mechanical connection linking the recuperation valve to the secondary piston comprises a pivoted lever which extends from the recuperation valve to engage a portion of the secondary piston located outside the secondary pressure chamber.
- the recuperation passage enters the bore at the point which is uppermost when the master cylinder is in its normal operating orientation. Since, in general, a master cylinder is located in a motor vehicle either horizontally, or slopping upwardly from the open end of the master cylinder to the closed end, the recuperation passage preferably enters the bore adjacent the closed end of the master cylinder and on the side of the bore adjacent the reservoir. With this arrangement, air bubbles tending to accumulate at the highest point of the secondary pressure chamber will automatically be bled to the reservoir when the recuperation valve is open.
- the mechanical connection between the secondary piston and the recuperation valve is in the form of a lever located substantially within the reservoir of the master cylinder.
- the end of the lever projects into the master cylinder bore and is engaged by a rearwardly facing flange of the secondary piston in the normal rest position of the master cylinder.
- the force imposed on the lever by the secondary piston holds the recuperation valve open.
- the recuperation valve is spring closed. If the secondary piston carries a pair of spaced apart seals, the end of, the lever can advantageously be located between the seals, and the flange which engages the lever may be the support flange of the front seal of the secondary piston.
- the space between the secondary piston seals is connected to that portion of the reservoir associated with the primary pressure chamber.
- the operating lever can conveniently be in the form of a pivoted bell-crank arrangement which extends from the bore through the portion of the reservoir associated with the primary pressure chamber, over the internal baffle of the reservoir and into the portion of the reservoir associated with the secondary pressure chamber for engagement with the recuperation valve.
- This arrangement may be further improved if the space between the two seals is connected to a recuperation valve housed within the secondary piston for supplying recuperation flow to the primary pressure chamber.
- the single primary piston seal is preferably mounted on the primary piston, thereby allowing a simple cylindrical master cylinder bore to be used and ensuring that the primary piston seal always runs on a wet surface during a pressure generating stroke.
- The, or each, recuperation valve is preferably in the form of a centre valve having an axially movable valve member incorporating an elastomeric seal for engaging the face of an associated valve seat.
- a tandem master cylinder 1 including a unitary cast body 2 to which is secured a moulded plastics reservoir 3.
- the body is formed with a smooth cylindrical bore 4 over the majority of its length.
- the bore is closed at one end by a wall 5 and at the other, open end is stepped outwardly to receive a seal and closure assembly 6.
- a primary piston 7 is slidably received by the assembly 6, and a secondary piston 8 is slidably mounted in the bore 4.
- the secondary piston has mounted thereon pressure seals 9, 10 whilst the primary piston 7 slides through a pressure seal 11 and an atmospheric seal 12 secured to the body 2.
- a primary pressure chamber 13 is defined between the primary piston 7 and secondary piston 8, and a secondary pressure chamber 14 is defined between the end wall 5 and the secondary piston 8.
- Outlet connections are provided to connect the chambers 13, 14 to respective brake circuits.
- the master cylinder 1 is effective to pressurise either circuit in the event of failure on the other circuit, but under normal circumstances provides equal pressure to each circuit.
- the reservoir 3 is divided into a first portion 15 associated with the primary pressure chamber and a second portion 16 associated with the secondary pressure chamber by a central baffle 17.
- the primary chamber 13 is connected to the reservoir portion 15 by way of radial ports 18 formed in the primary piston 7, a passage 19 defined within the assembly 6, a passage 20 defined in the valve body, and a chamber 21 formed in the master cylinder body at the base of the reservoir portion 15.
- a radial passage 22 connects the chamber 21 to the bore 2 in the zone 23 located between seals 9, 10. It will be appreciated that at the commencement of a pressure generating stroke the primary piston 7 moves forward to isolate ports 18 from the passage 19, and accordingly the normally open recuperation passage is closed.
- a recuperation passage between the secondary pressure chamber 14 and the reservoir portion 16 is provided by a recuperation passage 24 which extends from a port 25 in the wall of the bore 4 through a centre valve assembly 26 to the reservoir portion 16.
- the centre valve assembly 26 includes a valve member 27 which is biased by a valve spring 28 towards a closed position, but which in the normal rest position of the master cylinder is held open by a lever 29.
- the lever 29 is mounted for pivotal movement about an axis 30, and extends through the chamber 21 and port 22 into the region 23 of the bore 4. In the illustrated rest position the end of the lever 29 located in the bore portion 23 is engaged by a flange 31 of the secondary piston. Since the secondary piston 8 is biased to the right (as viewed in Figure 1) by a return spring 32, the lever 29 is biased anti-clockwise about pivot axis 30 to hold the valve member 27 clear of its associated seat and thus provide an open recuperation passage extending from the secondary chamber 14. Upon commencement of a pressure generating stroke the secondary piston 8 advances to relieve the force applied to the lever 29, thereby allowing the lever to be pivoted clockwise as the return spring 28 moves the valve member 27 into its closed position.
- the bore of the secondary chamber 14 houses no components whatsoever of the valve assembly 26 or associated operating lever 29.
- the overall length of the secondary chamber 14 can be reduced to the minimum required to provide adequate stroke movement for the piston 8.
- the interior surface of the end wall 5 does not require machining.
- the use of a self contained centre valve assembly 26 as illustrated in the drawing means that the only machining of the body necessary to provide a recuperation valve is the formation of a threaded passage for mounting the assembly 26, and even this minimal machining can readily be accomplished since the area to be machined is readily accessible to the exterior of the casting.
- the port 25 is located closely adjacent the end wall 5 and on the side of the bore 4 which is normally uppermost (by virtue of the necessity to have the reservoir upright).
- the master cylinder is located in the usual orientation, i.e. sloping somewhat upwards from right to left (as viewed in Figure 1), any bubbles of air accumulating at the highest point of the secondary chamber 14 will automatically be led to the reservoir 3.
- a further advantage of the master cylinder shown in Figure 1 lies in the fact that the diameter of the primary piston 7 is very slightly less than the diameter of the bore 4. This enables the service outlet passage from the primary chamber 13 to be located adjacent the pressure seal 11 since, even as the primary piston 7 advances to the point at which it overlies the service outlet, an annular passage will still be defined connecting the service outlet to the main part of the primary chamber 13, the annular passage being formed between the bore 4 and the external surface of the primary piston 7. This arrangement is particularly advantageous since it allows the spacing between the seals 10 and 11 (when the master cylinder is in the rest condition) to be reduced to less than the full stroke of the primary piston 7.
- the primary piston 7 can, in its fully advanced position, in part occupy the zone which in the rest condition of the master cylinder is located adjacent to or forward of the seal 10.
- recuperation valve assembly 26 and operating lever 29, together with the associated secondary pressure chamber 14 are substantially identical to the arrangements described in Figure 1 and will not be described again in detail.
- the recuperation passage associated with the primary chamber 13 is provided by means of a cross passage 34 provided in the secondary piston, an axial passage 35 provided in the secondary piston, and a centre valve arrangement 36 comprising a valve member 37 which engages a seat 38 formed on the secondary piston 8A.
- the valve member 37 is linked to the primary piston 7A by a headed stud 39 whereby the centre valve 36 is held open when the master cylinder is in the rest configuration, thereby defining a recuperation path for the primary chamber 13 via valve assembly 36, passage 35, passage 34, bore zone 23, passage 22, and chamber 21.
- the body bore 4A is of uniform cross-section throughout its length, the primary piston 7A being of equal diameter to the secondary piston 8A.
- complex machining of the bore 4 is totally eliminated, and aside from forming a smooth cylindrical bore of uniform diameter the only machining required associated with the bore is to form the radial ports 22 and 25, and the service outlet passages associated with the primary and secondary chambers.
- Figure 3 shows a third embodiment of the invention which is in large part similar to the embodiment of Figure 2.
- the reservoir 41 is in part defined by an annular wall 42 integral with the body casting, and in part defined by a moulded plastics cover 43 which is a push-fit over the wall 42.
- An O-ring seal 44 seals between the wall 42 and cover 43, and the normal fluid level is above the top of the wall 42.
- the cover 43 is held in position by one or more clips 45 which engage under bosses 45A on the body casting.
- the wall 42 is a right circular cylinder
- the cover 43 preferably includes a clip 46 which extends from the cover into engagement with the body to prevent rotation of the cover relative to the body.
- the wall 47 which divides the reservoir into primary and secondary portions is integral with the body casting as are one or more supports 48 which carry a pin 49 by means of which the lever 29 is rotatably mounted.
- the cover 43 is preferably translucent permitting the brake fluid level to be seen, and preferably carries the conventional marks indicating maximum and minimum permitted fluid levels.
- a fluid level warning indicator 50 is preferably included. It will be appreciated that the cover 43 may be designed to be an internal push-fit within the wall 42 under some circumstances. The above described reservoir arrangement may be of more general application than to the particular master cylinder shown.
- Figure 4 shows a pratical embodiment of the invention which is operationally identical to the embodiment of Figure 3.
- Figure 4 illustrates suitable practical outlet connections 51, 52 to connecting use circuits to the primary 13 and secondary 14 chambers respectively.
- the reservoir 53 of Figure 4 is somewhat different from that of Figure 3 in that the retaining clips 45 and associated bases 45A have been omitted, and the reservoir 53 is retained on the annular wall 42 by a worm-drive clamp 54.
- the reservoir 53 is taller than that of Figure 3 to give a larger reserve of fluid, and incorporates a modified fluid level warning indicator 55 to provide both mechanical and electrical warning of low fluid level.
Description
- This invention relates to a hydraulic master cylinder, and more particularly to a so-called "tandem" master cylinder in which two pistons are arranged in a common bore and pressurise separate primary and secondary pressure chambers which are connected to respective use circuits. Such master cylinders are commonly used in split circuit hydraulic brake systems of motor cars.
- A typical tandem master cylinder is shown in published British patent application GB 2030668A. Whilst such master cylinders work effectively they tend to be of considerable length which creates difficulties in housing the master cylinder in a motor car, and are of considerable weight, which is undesirable.
- As will be appreciated by those skilled in the art, it is of assistance in designing a tandem master cylinder having a shorter length than that shown in GB 2030668A if the normally open recuperation passage associated with the secondary pressure chamber opens into the secondary pressure chamber at the end thereof remote from the secondary piston. However, if the recuperation passage is placed at the end of the secondary pressure chamber remote from the secondary piston a valve arrangement must be provided for closing the recuperation passage during pressure generating strokes of the master cylinder, and a linkage must be provided to operate such valve, the linkage extending from the valve to the secondary piston. Arrangements of this type are shown in British patent specification GB 1289608A and published British patent application 2135412A. These prior art proposals suffer from a number of disadvantages.
- In the case of GB 2135412 the valve seat is directly machined on the internal end face of the master cylinder body assembly. Such machining is difficult to achieve with accuracy, and necessitates the provision of a connecting passage located within the thickness of the end wall of the master cylinder. This unnecessarily adds to the length and weight of the master cylinder. This problem is in part overcome in GB 1289608A since the recuperation passage is formed in the side-wall of the master cylinder, and the valve seat is formed on a separate end plug. However, it will be appreciated that the valve seat must be machined accurately over a relatively large area, and in particular must be exactly perpendicular to the master cylinder axis in order to ensure reliable sealing. Further the valve seat is particularly vulnerable to damage, e.g. by scratching, if the end plug is removed.
- The prior art suffers from the further disadvantage that the moving components of the recuperation valve, together with the associated springs and control linkage, are located within the portion of the main bore of the master cylinder which forms the secondary pressure chamber. This leads to three separate problems: firstly, the length of the secondary pressure chamber is liable to be increased by the need to house such components; secondly, since such components are located deep in the bore they render assembly of the master cylinder more difficult; and thirdly, since the movable member of the recuperation valve will have only minimal travel, lost motion between the secondary piston and the valve operating linkage must be provided for within the portion of the bore of the master cylinder which forms the secondary chamber. These problems are solved in the prior art by means of complex machining of the master cylinder bore and/or the use of a master cylinder body fabricated from a number of separate components. This is, of course, undesirable.
- A tandem master cylinder which overcomes some of the problems outlined above is illustrated in DE-B-2711297 (corresponding to the preamble of claim 1). In this master cylinder the recuperation passage associated with the second pressure chamber extends radially outwardly from the secondary chamber, and a recuperation valve is located outside the zone of the bore of the master cylinder. A mechanical connection extends from the recuperation valve into the main bore of the master cylinder to open the recuperation valve when the secondary piston is in its rest position. However, in order to engage the mechanical connection the secondary piston includes a forward extension which projects into the zone of the recuperation passage when the secondary piston is in its rest position. In order to accommodate this extension the main bore of the master cylinder must be correspondingly lengthened. In effect, the portion of the bore occupied by the secondary piston extension is unavailable for pressure generation, and merely adds to the overall length of the master cylinder.
- The present invention is characterized in that the mechanical connection linking the recuperation valve to the secondary piston comprises a pivoted lever which extends from the recuperation valve to engage a portion of the secondary piston located outside the secondary pressure chamber.
- With such an arrangement, the need for a secondary piston extension in the manner shown in DE-B-2711297 is avoided and the master, cylinder can be made correspondingly more compact.
- In the preferred embodiment of the invention the recuperation passage enters the bore at the point which is uppermost when the master cylinder is in its normal operating orientation. Since, in general, a master cylinder is located in a motor vehicle either horizontally, or slopping upwardly from the open end of the master cylinder to the closed end, the recuperation passage preferably enters the bore adjacent the closed end of the master cylinder and on the side of the bore adjacent the reservoir. With this arrangement, air bubbles tending to accumulate at the highest point of the secondary pressure chamber will automatically be bled to the reservoir when the recuperation valve is open.
- In a particularly preferred embodiment of the invention the mechanical connection between the secondary piston and the recuperation valve is in the form of a lever located substantially within the reservoir of the master cylinder. Conveniently, the end of the lever projects into the master cylinder bore and is engaged by a rearwardly facing flange of the secondary piston in the normal rest position of the master cylinder. The force imposed on the lever by the secondary piston holds the recuperation valve open. When the secondary piston moves forward during pressure generating strokes force on the lever is released and the recuperation valve is spring closed. If the secondary piston carries a pair of spaced apart seals, the end of, the lever can advantageously be located between the seals, and the flange which engages the lever may be the support flange of the front seal of the secondary piston. In this way the lost motion required between the lever and the secondary piston is provided by the space between the secondary piston seal support flanges. Since this space must, in any event, be provided to ensure the two pressure chambers are separated by a reservoir chamber, its use to accommodate lost motion is particularly desirable since it obviates the need to make any special provision for this purpose. Thus, the amount of machining needed is reduced, and the design generally simplified.
- In a particularly preferred arrangement the space between the secondary piston seals is connected to that portion of the reservoir associated with the primary pressure chamber. In this case, the operating lever can conveniently be in the form of a pivoted bell-crank arrangement which extends from the bore through the portion of the reservoir associated with the primary pressure chamber, over the internal baffle of the reservoir and into the portion of the reservoir associated with the secondary pressure chamber for engagement with the recuperation valve. This arrangement may be further improved if the space between the two seals is connected to a recuperation valve housed within the secondary piston for supplying recuperation flow to the primary pressure chamber. This not only provides a simple means of allowing for recuperation flow to the primary pressure chamber, but offers the further advantage that only a single seal need be provided for the primary piston, as opposed to the two seals usually provided. The single primary piston seal is preferably mounted on the primary piston, thereby allowing a simple cylindrical master cylinder bore to be used and ensuring that the primary piston seal always runs on a wet surface during a pressure generating stroke.
- The, or each, recuperation valve is preferably in the form of a centre valve having an axially movable valve member incorporating an elastomeric seal for engaging the face of an associated valve seat.
- The above and other features and advantages of the invention will become clear from the following description of preferred embodiments thereof given by way of example only, reference being had to the accompanying drawings wherein:
- Figure 1 illustrates an axial cross-section of a first embodiment of the invention and
- Figures 2-4 are views corresponding to Figure 1 of second, third and fourth embodiments of the invention.
- Referring firstly to Figure 1 there is shown a tandem master cylinder 1 including a
unitary cast body 2 to which is secured a mouldedplastics reservoir 3. The body is formed with a smoothcylindrical bore 4 over the majority of its length. The bore is closed at one end by awall 5 and at the other, open end is stepped outwardly to receive a seal andclosure assembly 6. Aprimary piston 7 is slidably received by theassembly 6, and asecondary piston 8 is slidably mounted in thebore 4. The secondary piston has mounted thereonpressure seals primary piston 7 slides through apressure seal 11 and anatmospheric seal 12 secured to thebody 2. - A
primary pressure chamber 13 is defined between theprimary piston 7 andsecondary piston 8, and asecondary pressure chamber 14 is defined between theend wall 5 and thesecondary piston 8. Outlet connections (not shown) are provided to connect thechambers - The
reservoir 3 is divided into afirst portion 15 associated with the primary pressure chamber and asecond portion 16 associated with the secondary pressure chamber by a central baffle 17. When the master cylinder is in the illustrated rest position theprimary chamber 13 is connected to thereservoir portion 15 by way ofradial ports 18 formed in theprimary piston 7, apassage 19 defined within theassembly 6, apassage 20 defined in the valve body, and achamber 21 formed in the master cylinder body at the base of thereservoir portion 15. Aradial passage 22 connects thechamber 21 to thebore 2 in thezone 23 located betweenseals primary piston 7 moves forward toisolate ports 18 from thepassage 19, and accordingly the normally open recuperation passage is closed. - A recuperation passage between the
secondary pressure chamber 14 and thereservoir portion 16 is provided by arecuperation passage 24 which extends from aport 25 in the wall of thebore 4 through acentre valve assembly 26 to thereservoir portion 16. Thecentre valve assembly 26 includes avalve member 27 which is biased by avalve spring 28 towards a closed position, but which in the normal rest position of the master cylinder is held open by alever 29. - The
lever 29 is mounted for pivotal movement about anaxis 30, and extends through thechamber 21 andport 22 into theregion 23 of thebore 4. In the illustrated rest position the end of thelever 29 located in thebore portion 23 is engaged by aflange 31 of the secondary piston. Since thesecondary piston 8 is biased to the right (as viewed in Figure 1) by a return spring 32, thelever 29 is biased anti-clockwise aboutpivot axis 30 to hold thevalve member 27 clear of its associated seat and thus provide an open recuperation passage extending from thesecondary chamber 14. Upon commencement of a pressure generating stroke thesecondary piston 8 advances to relieve the force applied to thelever 29, thereby allowing the lever to be pivoted clockwise as thereturn spring 28 moves thevalve member 27 into its closed position. - It will be noted that the bore of the
secondary chamber 14 houses no components whatsoever of thevalve assembly 26 or associatedoperating lever 29. Thus, there is no necessity to assemble complex or small components within thechamber 14, and there are no such components impeding the stroke movement of thesecondary piston 8. Accordingly, the overall length of thesecondary chamber 14 can be reduced to the minimum required to provide adequate stroke movement for thepiston 8. Further, the interior surface of theend wall 5 does not require machining. In fact, the use of a self containedcentre valve assembly 26 as illustrated in the drawing means that the only machining of the body necessary to provide a recuperation valve is the formation of a threaded passage for mounting theassembly 26, and even this minimal machining can readily be accomplished since the area to be machined is readily accessible to the exterior of the casting. - It will further be noted that the
port 25 is located closely adjacent theend wall 5 and on the side of thebore 4 which is normally uppermost (by virtue of the necessity to have the reservoir upright). Thus, if the master cylinder is located in the usual orientation, i.e. sloping somewhat upwards from right to left (as viewed in Figure 1), any bubbles of air accumulating at the highest point of thesecondary chamber 14 will automatically be led to thereservoir 3. - A further advantage of the master cylinder shown in Figure 1 lies in the fact that the diameter of the
primary piston 7 is very slightly less than the diameter of thebore 4. This enables the service outlet passage from theprimary chamber 13 to be located adjacent thepressure seal 11 since, even as theprimary piston 7 advances to the point at which it overlies the service outlet, an annular passage will still be defined connecting the service outlet to the main part of theprimary chamber 13, the annular passage being formed between thebore 4 and the external surface of theprimary piston 7. This arrangement is particularly advantageous since it allows the spacing between theseals 10 and 11 (when the master cylinder is in the rest condition) to be reduced to less than the full stroke of theprimary piston 7. In effect, because the outlet from theprimary pressure chamber 13 is located as described above, theprimary piston 7 can, in its fully advanced position, in part occupy the zone which in the rest condition of the master cylinder is located adjacent to or forward of theseal 10. This contrast with the arrangement of, for example, GB 2030668A in which the primary piston cannot advance into a zone of the master cylinder bore previously occupied by the secondary piston rear seal because of the service outlet port from the primary pressure chamber. Even if such service outlet port were to be located close to the rear seal of the secondary piston in the arrangement illustrated in GB 2030668A the forward movement of the primary piston is limited by the need to keep the service outlet port forwardly of the front seal on the primary piston. - The combined effect of the proposals outlined above is to enable a particularly compact master cylinder to be produced as will be clearly visible from a comparison of Figure 1 of the present application with Figure 1 of GB 2030668A.
- Referring now to Figure 2 the
recuperation valve assembly 26 and operatinglever 29, together with the associatedsecondary pressure chamber 14 are substantially identical to the arrangements described in Figure 1 and will not be described again in detail. However, in the Figure 2 arrangement the recuperation passage associated with theprimary chamber 13 is provided by means of across passage 34 provided in the secondary piston, anaxial passage 35 provided in the secondary piston, and acentre valve arrangement 36 comprising avalve member 37 which engages aseat 38 formed on thesecondary piston 8A. Thevalve member 37 is linked to theprimary piston 7A by a headedstud 39 whereby thecentre valve 36 is held open when the master cylinder is in the rest configuration, thereby defining a recuperation path for theprimary chamber 13 viavalve assembly 36,passage 35,passage 34, borezone 23,passage 22, andchamber 21. - It will also be noted that in Figure 2 the body bore 4A is of uniform cross-section throughout its length, the
primary piston 7A being of equal diameter to thesecondary piston 8A. Thus, complex machining of thebore 4 is totally eliminated, and aside from forming a smooth cylindrical bore of uniform diameter the only machining required associated with the bore is to form theradial ports - Finally, it will be noted that in Figure 2 only a
single seal 40 is provided on theprimary piston 7A. This considerably shortens the length of the piston and is possible because thevalve assembly 36 obviates the need to provide two seals for the primary piston as required in conventional designs of the type shown in GB 2030668A. Because theseal 40 is mounted on the piston, it always runs on a surface wet with brake fluid during pressure generating strokes which, as will be well understood, is desirable. - Figure 3 shows a third embodiment of the invention which is in large part similar to the embodiment of Figure 2. However, in Figure 3 the reservoir 41 is in part defined by an
annular wall 42 integral with the body casting, and in part defined by a moulded plastics cover 43 which is a push-fit over thewall 42. An O-ring seal 44 seals between thewall 42 and cover 43, and the normal fluid level is above the top of thewall 42. The cover 43 is held in position by one ormore clips 45 which engage underbosses 45A on the body casting. If,. as is preferred, thewall 42 is a right circular cylinder, the cover 43 preferably includes a clip 46 which extends from the cover into engagement with the body to prevent rotation of the cover relative to the body. - The
wall 47 which divides the reservoir into primary and secondary portions is integral with the body casting as are one ormore supports 48 which carry apin 49 by means of which thelever 29 is rotatably mounted. - The cover 43 is preferably translucent permitting the brake fluid level to be seen, and preferably carries the conventional marks indicating maximum and minimum permitted fluid levels. A fluid
level warning indicator 50 is preferably included. It will be appreciated that the cover 43 may be designed to be an internal push-fit within thewall 42 under some circumstances. The above described reservoir arrangement may be of more general application than to the particular master cylinder shown. - Finally, Figure 4 shows a pratical embodiment of the invention which is operationally identical to the embodiment of Figure 3. Figure 4, however, illustrates suitable
practical outlet connections reservoir 53 of Figure 4 is somewhat different from that of Figure 3 in that the retaining clips 45 and associatedbases 45A have been omitted, and thereservoir 53 is retained on theannular wall 42 by a worm-drive clamp 54. Thereservoir 53 is taller than that of Figure 3 to give a larger reserve of fluid, and incorporates a modified fluidlevel warning indicator 55 to provide both mechanical and electrical warning of low fluid level.
Claims (6)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB848425106A GB8425106D0 (en) | 1984-10-04 | 1984-10-04 | Hydraulic master cylinder |
GB8425106 | 1984-10-04 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0177346A2 EP0177346A2 (en) | 1986-04-09 |
EP0177346A3 EP0177346A3 (en) | 1986-12-10 |
EP0177346B1 true EP0177346B1 (en) | 1989-03-15 |
Family
ID=10567709
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85307060A Expired EP0177346B1 (en) | 1984-10-04 | 1985-10-02 | Hydraulic master cylinder |
Country Status (7)
Country | Link |
---|---|
US (1) | US4688382A (en) |
EP (1) | EP0177346B1 (en) |
JP (1) | JPS61160345A (en) |
AU (1) | AU577624B2 (en) |
BR (1) | BR8504888A (en) |
DE (1) | DE3568747D1 (en) |
GB (2) | GB8425106D0 (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH04116275U (en) * | 1991-03-30 | 1992-10-16 | アイシン精機株式会社 | master cylinder |
US5477681A (en) * | 1994-11-14 | 1995-12-26 | Kelsey-Hayes Company | Dual center-port master cylinder |
US5542253A (en) * | 1995-02-21 | 1996-08-06 | Kelsey-Hayes Company | Vehicular braking system having a low-restriction master cylinder check valve |
DE19653270B4 (en) * | 1996-12-20 | 2008-01-03 | Zf Sachs Ag | Master cylinder for hydraulic actuation systems |
US6705083B2 (en) * | 2001-07-31 | 2004-03-16 | Delphi Technologies, Inc. | Master cylinder having a compact profile |
DE10222865B4 (en) * | 2002-05-23 | 2004-04-15 | Lucas Automotive Gmbh | master cylinder |
JP2005104332A (en) * | 2003-09-30 | 2005-04-21 | Hitachi Ltd | Master cylinder device |
DE102005008722B4 (en) * | 2005-02-25 | 2008-07-31 | Lucas Automotive Gmbh | Master cylinder with lever-operated valve |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB410243A (en) * | 1932-12-15 | 1934-05-17 | Frederick Henry Royce | Improvements in cylinders for hydraulic systems |
US2282390A (en) * | 1939-03-20 | 1942-05-12 | Kelseyhayes Wheel Company | Master cylinder |
US2657537A (en) * | 1950-10-26 | 1953-11-03 | Gen Motors Corp | Master cylinder with compensating valve |
US3044268A (en) * | 1960-11-17 | 1962-07-17 | Bendix Corp | High pumping efficiency master cylinder |
CA1066329A (en) * | 1976-03-16 | 1979-11-13 | Edward J. Falk | Tandem brake master cylinder |
US4295322A (en) * | 1979-10-15 | 1981-10-20 | Nordson Corporation | Tube forming shoe and methods of forming a flexible web into a tube |
JPS595642Y2 (en) * | 1980-12-26 | 1984-02-20 | アイシン精機株式会社 | master cylinder |
US4407121A (en) * | 1981-04-29 | 1983-10-04 | The Bendix Corporation | Master cylinder |
-
1984
- 1984-10-04 GB GB848425106A patent/GB8425106D0/en active Pending
-
1985
- 1985-09-30 US US06/781,879 patent/US4688382A/en not_active Expired - Fee Related
- 1985-10-01 AU AU48163/85A patent/AU577624B2/en not_active Ceased
- 1985-10-02 DE DE8585307060T patent/DE3568747D1/en not_active Expired
- 1985-10-02 GB GB08524267A patent/GB2165327B/en not_active Expired
- 1985-10-02 EP EP85307060A patent/EP0177346B1/en not_active Expired
- 1985-10-03 BR BR8504888A patent/BR8504888A/en not_active IP Right Cessation
- 1985-10-04 JP JP60221699A patent/JPS61160345A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
EP0177346A2 (en) | 1986-04-09 |
GB2165327A (en) | 1986-04-09 |
JPS61160345A (en) | 1986-07-21 |
DE3568747D1 (en) | 1989-04-20 |
GB2165327B (en) | 1988-05-25 |
US4688382A (en) | 1987-08-25 |
BR8504888A (en) | 1986-07-22 |
JPH0554467B2 (en) | 1993-08-12 |
AU577624B2 (en) | 1988-09-29 |
AU4816385A (en) | 1986-04-10 |
EP0177346A3 (en) | 1986-12-10 |
GB8425106D0 (en) | 1984-11-07 |
GB8524267D0 (en) | 1985-11-06 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0177346B1 (en) | Hydraulic master cylinder | |
US4455832A (en) | Master cylinder | |
US3914943A (en) | Return manifold for hydraulic brake actuator | |
US4475338A (en) | Master cylinder | |
US20060157141A1 (en) | Container for hydraulic medium supply | |
EP0130297B1 (en) | Fast-fill master cylinder | |
EP0074874B1 (en) | Fast-fill master cylinder | |
US3064432A (en) | Master cylinder construction | |
US5046316A (en) | Tandem master cylinder with filters arranged in central valves | |
CA2483179C (en) | Fuel return valve | |
JPS595642Y2 (en) | master cylinder | |
EP0088019B1 (en) | Master cylinder | |
US3044268A (en) | High pumping efficiency master cylinder | |
US4807438A (en) | Reservoir inlet assembly for a master cylinder | |
US4499730A (en) | Automotive tandem type master cylinder | |
JPH0141643Y2 (en) | ||
JPS5843481Y2 (en) | tandem master cylinder | |
KR100246132B1 (en) | Brake booster | |
JPS599967Y2 (en) | Tandem type master cylinder | |
JP2748634B2 (en) | Reservoir tank for master cylinder | |
JP2562115Y2 (en) | Liquid level alarm device for reservoir | |
JP3751050B2 (en) | Master cylinder and reservoir assembly | |
JPH0416766Y2 (en) | ||
JPS6238431Y2 (en) | ||
JPS6312023B2 (en) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FR IT |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE FR IT |
|
17P | Request for examination filed |
Effective date: 19870123 |
|
17Q | First examination report despatched |
Effective date: 19871207 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR IT |
|
ITF | It: translation for a ep patent filed |
Owner name: ING. A. GIAMBROCONO & C. S.R.L. |
|
REF | Corresponds to: |
Ref document number: 3568747 Country of ref document: DE Date of ref document: 19890420 |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
ITTA | It: last paid annual fee | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19931011 Year of fee payment: 9 Ref country code: DE Payment date: 19931011 Year of fee payment: 9 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Effective date: 19950630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19950701 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |